The present disclosure relates to wind turbine generators including wind turbine rotatable assemblies.

Rotatable parts in wind turbine applications involve high radial and axial loadings. In such applications, reduced or no slip is required between the rotatable parts to minimize wear over long periods of service. For this purpose, specific bearing systems are commonly used arranged between the rotatable parts. An example of wind turbine rotatable parts is the rotor and stator of the electrical generator.

In such wind turbine applications, the use of bearing systems comprising tapered roller bearings is known in the art, such as for example the bearing system disclosed in EP2360383. The tapered roller bearings are arranged in several rows, typically in pairs of rows such as for example two or four rows, such that a compact structure is obtained for effectively handling axial and radial loads while providing high levels of stiffness.

Associated with such wind turbine bearing systems is a lubricant chamber. The lubricant chamber is typically formed around the roller bearings so that they are suitably greased in order to reduce friction and prevent corrosion.

The lubricant chamber is conveniently sealed through suitable seal. Examples of a suitable seal is labyrinth seals, rubber lips, and the like.

In standard configurations, the seal is usually arranged between a bearing outer ring and a bearing inner ring. The bearing inner ring in this case usually comprises two rings each supporting a bearing race. The seal is usually fixed to the rotating bearing outer ring and further arranged to slidingly contact the inner bearing outer ring so as to form a sealed chamber between both rings.

As used herein, a bearing outer ring refers to that having diameter larger than that of the bearing inner ring.

The above bearing systems suffer from the disadvantage of high structural complexity, so there is a need for reducing the number of parts involved while still preventing the rings to be undesirably oversized.

A wind turbine generator has been developed with which the above disadvantages are at least partially reduced while also providing advantageous effects. The present assembly has been shown to be an efficient solution for large electric generators in direct drive wind turbines.

The present wind turbine generator includes a rotatable assembly that comprises a first part, a second part and a third part.

The first part is a fixed part such as for example the stator of an electrical generator.

The second part is a rotatable part comprising a generator rotor.

The third part of the present wind turbine rotatable assembly comprises a wind turbine bearing system. The bearing system comprises at least one outer ring, at least one inner ring, and at least one bearing element. The at least one bearing element is arranged between the outer and inner rings. The bearing element may for example comprise one or more tapered roller bearings. Other bearings may of course be used.

The inner ring is associated with one of the first part and the second part and the outer ring is associated with the other of the first part and the second part. Thus, in one example the outer ring may be associated both with the bearing system and the second rotatable part.

A lubricant chamber is also provided intended to properly grease the bearing system in order to reduce friction and to prevent corrosion. The lubricant chamber may be formed, for example, between the first part and the bearing system. The lubricant chamber is conveniently sealed through a suitable seal.

According to an important feature of the present wind turbine generator, the seal is part of or is directly attached to the electrical generator rotor for sealing the lubricant chamber. The seal is arranged between the second, rotatable part and the bearing system. In some examples, at least one cover may be also provided for at least partially covering the seal.

The seal may comprise at least one sealing element that is directly attached to the electrical generator rotor. Such sealing element may comprise, for example a rubber element. Other seals may be of course used to act as sealing element.

As used herein, the feature that the seal is part of the electrical generator rotor refers to an integral configuration of the seal with the electrical generator rotor. On the other hand, also as used herein, directly attached refers to a connection of the seal, or the sealing element (e.g. rubber element), to the electrical generator rotor that does not include any intervening parts.

At least one outlet for the lubricant may be further included. Such outlet may be formed in the second part, that is, the electrical generator rotor, so that the lubricant comes out of the lubricant chamber.

The above described rotatable assembly advantageously allows the integration of seal especially in two row tapered roller bearings between a bearing ring and surrounding parts in a wind turbine. Advantageously, the electrical generator rotor acts as a sealing carrier and the lubricant outlet can be formed in the electrical generator rotor, sandwiched with surrounding parts. This results in a further important advantage relating to significant savings in material which has been found to have a cost impact of the order of around 10%.

The above rotatable assembly may find application especially in large generators as those used in direct-drive wind turbines and, for more particularly, in large permanent magnet generators.

Furthermore, the above rotatable assembly may find application in the wind turbine main bearing. Thus, the present disclosure also relates to wind turbines including the above described rotatable assembly, comprising a first part, a second part that can rotate relative to the first part, a bearing system arranged between said first and second parts and comprising one or more bearing elements, a lubricant chamber, and a seal that is part of or is directly attached to the second part for sealing said lubricant chamber wherein the first part is the main frame of the wind turbine and the second part is a wind turbine rotor, i.e. hub and blades.

Additional objects, advantages and features of examples of the present wind turbine generator will become apparent to those skilled in the art upon examination of the description, or may be learned by practice thereof.

One example of the present wind turbine generator will be described in the following by way of non-limiting examples. The present example is given with reference to the appended drawing where a permanent magnet generator for a wind turbine is illustrated including the present rotatable assembly.

In the drawing, a permanent magnet generator for a wind turbine is shown comprising a rotatable assembly 100. The rotatable assembly 100 comprises a fixed, first part 200, a rotatable, second part 300 and a third part 400.

The fixed, first part 200 is associated with a stator of an electrical generator.

The rotatable, second part 300 is part of the rotor 360 of an electrical generator. The second part 300 can rotate relative to the fixed, first part 200.

The third part 400 comprises a wind turbine bearing system 420. The wind turbine bearing system 420 comprises an outer ring 430, an inner ring 440, and a bearing element 450 that is arranged between the outer and inner rings 430, 440. The wind turbine bearing system 420 allows rotation between the first and second parts 200, 300.

In general, the inner ring 440 is associated with one of the first, fixed part 200 and the second part 300 while the outer ring 430 is associated with the other of the first 200 part and the second part 300. In the particular example shown in the drawing, the inner ring 440 is associated with the first, fixed part 200, while the outer ring 430 is associated with the second part 300. Thus, the outer ring 430 is both associated with the second part 300 and the bearing element 450. In the example shown, the outer ring 430, which is part of the third part 400, is provided between the second part or rotor 300 and the bearing elements 450.

The bearing system 420 comprises a number of tapered roller bearings 450 arranged in fluid communication with a lubricant chamber 500. The lubricant chamber 500 is formed between the inner ring 440 of the bearing system 420 and the second part 300. An outlet 550 is formed in the second part 300 for the lubricant to come out of the lubricant chamber 500.

A seal 600 is provided for sealing the lubricant chamber 500. The seal 600 is arranged between the second, rotatable part 300 and the bearing system 420 and, more particularly, between the rotatable part 300 and the inner ring 440. They comprise a sealing element 650, such as a rubber element, that is directly attached to the second part 300 of the rotatable assembly 100. Thus, the seal 600 and the outlet 550 both belong to the electrical generator rotor 360. As a consequence, the second rotatable part 300 in the present rotatable assembly 100 does perform a sealing function as opposed to prior art assemblies in which said sealing function is achieved within the bearing system 420 itself. Due to the particular configuration of the present rotatable assembly 100, the electrical generator rotor 360 is the part of the wind turbine that performs the sealing function for the lubricant chamber 500.

The rubber element 650 is connected to the second part 300 with no intervening parts. It could be also possible that the rubber element 650 is formed integrally with the second part 300. A cover 700 is provided for covering the sealing element 650 of the seal 600. The cover 700, together with the lubricant chamber 500 and the seal 600 are part of the second part 300.

Although only a particular embodiment of the present wind turbine generator has been disclosed herein, it will be understood by those skilled in the art that other alternative examples and/or uses and obvious modifications and equivalents thereof are possible. The present disclosure thus covers all possible combinations of the particular example described herein so its scope should not be limited by said example but should be determined only by a fair reading of the appended claims.